Catalytic chain transfer is an effective way to control the molecular weight of polymers of methacrylates and styrenes. It is known that chain transfer catalysis (CTC) products contain a terminal vinylidene bond. This feature makes these products attractive as macromonomers for a variety of applications. However, CTC has not been known to be applicable for reduction of molecular weight in the polymerizations of other vinylic monomers such as acrylates.
Copolymerizations of methacrylate monomers with monosubstituted monomers in the presence of cobalt have been described in the art. However, the monosubstituted monomer is almost always present as a minor component. U.S. Pat. No. 4,680,354 describes molecular weight reduction using various Co(II) complexes in MMA-BA, MMA-EA and MMA-BA-St copolymerizations, wherein the abbreviations represent:
MMA=methyl methacrylate
BA=butyl acrylate
EA=ethyl acrylate
St=styrene.
U.S. Pat. No. 5,324,879 describes molecular weight reduction with Co(III) complexes in EA, St, and vinyl acetate (VAc) polymerizations, and MMA-EA copolymerization.
U.S. Pat. No. 4,680,352 describes molecular weight reduction and macromonomer (polymers or copolymers with unsaturated end-groups) synthesis in copolymerizations with acrylates and styrene with various Co(II) complexes. Various terpolymerizations are cited therein; however, no evidence of the nature or existence of terminal double bonds is given.
Gruel et al., Polymer Preprints, 1991, 32, p. 545, reports the use of Co(II) cobaloximes in low conversion St-MMA copolymerizations at low temperatures with end group analysis.
The references cited above cover the copolymerization of acrylates and styrene with methacrylate monomers, but do not disclose synthetic conditions for production of high purity macromonomers based on acrylates and styrene, nor branching of the resulting products. The conditions disclosed are unlikely to yield high purity macromonomers for systems composed predominantly of monosubstituted monomers. Disclosed temperatures of less than 80xc2x0 C. are likely to provide substantial amounts of undesired graft copolymer at high conversion rates.
This invention concerns an improvement in a process for the free-radical polymerization of at least two unsaturated monomers to form a polymer whose molecular architecture comprises properties of molecular weight, branching, and vinyl-terminated end groups, the monomers having the formula
CH2xe2x95x90CXY 
wherein
X is selected from the group consisting of H, CH3, and CH2OH;
Y is selected from the group consisting of OR, O2CR, halogen, CO2H, COR, CO2R, CN, CONH2, CONHR, CONR2 and Rxe2x80x2;
R is selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, substituted and unsubstituted aralkyl, substituted and unsubstituted alkaryl, and substituted and unsubstituted organosilyl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid and halogen; and the number of carbons in said alkyl groups is from 1 to 12; and
Rxe2x80x2 is selected from the aromatic group consisting of substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid, substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted olefin and halogen;
by contacting said monomers with a cobalt-containing chain transfer agent and a free radical initiator at a temperature from about 80xc2x0 to 170xc2x0 C.;
the improvement which comprises controlling polymer architecture by introducing into the presence of the chain transfer agent at least one each of monomers A and B in the molar ratio of A:B, said molar ratio lying in the range of about 1,000:1 to 2:1, wherein for monomer A X is H and for monomer B X is methyl or hydroxymethyl; by one or more of the following steps:
I decreasing the ratio of A:B from about 1,000:1 toward 2:1;
II increasing the temperature from above 80xc2x0 C. toward 170xc2x0 C.;
III increasing the conversion of monomer to polymer toward 100% from less than about 50%;
IV decreasing the ratio of the chain transfer constant of A:B to below 1; and
V increasing the concentration of cobalt chain transfer agent;
whereby:
to effect lower molecular weight, employ at least one of steps I, II, IV and V;
to effect a higher degree of vinyl-terminated end groups, employ at least one of steps I, II, IV, and V; and
to effect increased branching, employ at least one of steps I, II, IV, and V with step III.
The nature of the derived products changes as a function of time. In the initial stages, linear macromonomers with one monomer-A in the terminal position can be obtained as essentially the only product. If the cobalt CTC catalyst levels are relatively low then CTC does not occur after every B-monomer insertion and the product mixture can include monomer-B units in the polymer chain as well as in the terminal position.
Cobalt chain transfer agent is employed in the form of cobalt complexes. Their concentrations are provided in the Examples in terms of ppm by weight of total reaction mass. Concentration will vary from 10 ppm to 1,500 ppm, preferably 10 to 1,000 ppm.
Later in the course of the reaction, when the concentration of the two above products is increased, then they can be reincorporated into a growing polymer chain. Thus, mono-branched product is obtained in the later stages of the reaction, usually around 90% conversion. At conversions above 95%, branches begin to appear on the branches, and the polymer becomes hyperbranched as conversions approach 100%.
Preferred monomers A are selected from the group consisting of acrylates, acrylonitrile and acrylamides;
and preferred monomers B are selected from the group:
a) substituted or unsubstituted xcex1-methylstyrenes;
b) substituted or unsubstituted alkyl methacrylates, where alkyl is C1-C12;
c) methacrylonitrile;
d) substituted or unsubstituted methacrylamide;
e) 2-chloropropene,
f) 2-fluoropropene,
g) 2-bromopropene,
h) methacrylic acid,
i) itaconic acid,
j) itaconic anhydride, and
k) substituted or unsubstituted styrenics.
If branched polymers are the desired product, it is possible to initiate the described process in the presence of preformed macromonomers. They can be of the type described in this patent. They can also be macromonomers based entirely upon methacrylates or the related species described previously in U.S. Pat. No. 4,680,354. Such a process would lead to products fitting the description above, but would allow for greater control over the polymer end-groups.
The branched polymers made by said process are polymers of this invention having the formula: 
Y is as earlier defined;
n=1-20, m=1-5, p=1-20,and n+m+pxe2x89xa73, and
Z is selected from the group CH2CHYCH3, CH2CMeYCH3, and, optionally, 
mxe2x80x2=0-5, pxe2x80x2=0-20; n+mxe2x80x2+pxe2x80x2xe2x89xa72;
and if m or mxe2x80x2 greater than 1, the m or mxe2x80x2 insertions respectively are not consecutive.
This invention also concerns a process comprising selecting A and B so the ratio of their chain transfer constants is less than 1, whereby functionality derived from Monomer B will be located on the vinyl-terminated end of the polymer.
This invention also concerns an improved process for the free-radical polymerization of at least two unsaturated monomers having the formula
CH2xe2x95x90CXY 
wherein
X is selected from the group consisting of H, CH3, and CH2OH;
Y is selected from the group consisting of OR, O2CR, halogen, CO2H, CO2R, CN, CONH2, CONHR, CONR2, COR and Rxe2x80x2;
R is selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, substituted and unsubstituted aralkyl, substituted and unsubstituted alkaryl, and substituted and unsubstituted organosilyl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid and halogen, and the number of carbons in said alkyl groups is from 1 to 12; and
Rxe2x80x2 is selected from the aromatic group consisting of substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted olefin and halogen;
by contacting said monomers with a cobalt-containing chain transfer agent and a free radical initiator at a temperature from about 80xc2x0 C. to 170xc2x0 C.;
the improvement which comprises controlling molecular weight of the polymer architecture by introducing into the presence of the chain transfer agent at least one each of monomers C and D in the molar ratio of C:D in the range of about 1,000:1 to 2:1, in which for monomer C, X is H and Yxe2x89xa0Rxe2x80x2 and for monomer D, X is H and Yxe2x95x90Rxe2x80x2 by:
decreasing the ratio of C:D from about 1,000:1 toward 2:1; or
increasing the temperature from above 80xc2x0 C. toward 170xc2x0 C.
Preferred monomers C are selected from the group consisting of acrylates, acrylonitrile and acrylamides;
and preferred monomers D are substituted and unsubstituted styrenics.
The polymers made by said process improvement are polymers of this invention having the formula: 
where Yxe2x89xa0Rxe2x80x2 and nxe2x89xa71.
This invention also concerns a process improvement for polymerizing monomer(s) in the presence of an excess of a nonpolymerizable olefin, Y1Y2Cxe2x95x90CY3Y4. The product in the initial stages of the polymerization will be composed primarily of 
wherein:
Y1 and Y3, and optionally Y2 and Y4, are each independently selected from the group consisting of xe2x80x94CH(O), xe2x80x94CN, xe2x80x94C(O)OR5, xe2x80x94C(O)NR6R7, xe2x80x94CR8(O), alkyl, aryl, substituted alkyl, substituted aryl; or
where Y1 and Y3 or Y2 and Y4 are combined in a cyclic structure which includes any of the above functionalities, or can be xe2x80x94C(O)xe2x80x94(CH2)xxe2x80x94, xe2x80x94C(O)xe2x80x94Oxe2x80x94(CH2)xxe2x80x94, xe2x80x94C(O)Oxe2x80x94C(O)xe2x80x94, xe2x80x94C(O)(CH2)xxe2x80x94, xe2x80x94C(O)NR9xe2x80x94(CH2)xxe2x80x94, wherein x=1-12, R5,R6,R7,R8, or R9 are hydrogen, alkyl, aryl, substituted alkyl, or substituted aryl; and where at least one of Y1 and Y3 is selected from the group consisting of xe2x80x94CH(O), xe2x80x94CN, xe2x80x94C(O)OR5, xe2x80x94C(O)NR6R7, xe2x80x94CR8(O), aryl, substituted aryl; and the remaining of Y2 and Y4 are xe2x80x94H.
The polymers made by said process improvement are polymers of this invention produced at later stages of the polymerization process having the formula: 
k=0 or 1, n=0-20, m=0-5, p=0-20; and k+n+m+pxe2x89xa72; if m greater than 1, then it is not intended to imply that the m insertions are consecutive;
Y is selected from the group consisting of OR, O2CR, halogen, CO2H, COR, CO2R, CN, CONH2, CONHR, CONR2 and Rxe2x80x2; and
Y1 to Y4 and R, and Rxe2x80x2 are as defined above.
We have discovered that, with addition of small amounts of an xcex1-methylvinyl monomer and appropriate choice of reaction conditions, polymerization of monosubstituted monomers in the presence of a metal complex can provide high yield of macromonomers. These macromonomers can subsequently be used for the synthesis of a wide range of block and graft copolymers.
This invention concerns a method for the synthesis of xcfx89-unsaturated macromonomers composed predominantly of monosubstituted monomers. The macromonomers are prepared by polymerizing a monosubstituted monomer as the major component (for example styrene) in the presence of a disubstituted xcex1-methylvinyl monomer (for example, xcex1-methylstyrene, herein also referred to as xe2x80x9cAMSxe2x80x9d) and a catalytic amount of a cobalt complex [for example, Co(II)(DMG-BF2)2] called CoII in Scheme 1. Reaction Scheme 1 illustrates the process where monomer A=styrene and monomer B=xcex1-methylstyrene. The process is applicable to a wide range of monosubstituted monomers (for example acrylate esters, vinyl acetate (VAc)) and other non-xcex1-methylvinyl monomers. 
In Scheme 1, xe2x80x9cPhxe2x80x9d represents a phenyl group, and xe2x80x9cmxe2x80x9d designates the number of monomer units in the polymer, and is xe2x89xa71.
The key features of the invention are the addition of small amounts of xcex1-methylvinyl monomers and the use of high reaction temperatures in the presence of chain transfer catalysts.
The incorporation of xcex1-methylvinyl monomers into the recipe allows formation of the desired macromonomer end group. In the absence of the xcex1-methylvinyl monomer, polymerization of monosubstituted monomers give polymers with internal double bonds (styrenic monomer) or a stable alkyl-cobalt species (acrylate monomers) as chain ends.
The use of high reaction temperatures ( greater than 100xc2x0 C.) favors the formation of pure linear macromonomers from monosubstituted monomers (for example acrylates, vinyl esters, and styrene). At lower temperatures we have shown that the formed macromonomers can react further by copolymerization to give branched polymers. Even though the macromonomers can undergo further reaction, at reaction temperatures  greater than 100xc2x0 C., the radicals so formed do not propagate to give branched polymers. Rather, they fragment to give back a macromonomer. It is possible that this chemistry will also reduce the polydispersity of the final product.
The invention also provides a route to block or graft copolymers as illustrated in Scheme 2. The product derived by copolymerization of the macromonomer in the presence of monomers can be determined by appropriate choice of the monomer and the reaction conditions. 
In Scheme 2, xe2x80x9cPhxe2x80x9d represents a phenyl group; xe2x80x9cmxe2x80x9d, xe2x80x9cnxe2x80x9d and xe2x80x9coxe2x80x9d designate the number of monomer units in the polymer; and X and Y are as defined above.
We have demonstrated that styrene macromonomers prepared by the above mentioned copolymerization route give chain transfer (by an addition fragmentation mechanism) and have acceptable chain transfer constants at temperatures  greater than 100xc2x0 C. They should therefore be useful in the preparation of block copolymers.
One further aspect of the invention is that by appropriate choice of the xcex1-methylvinyl monomer the method is also a route to end-functional polymers. For example, use of a hydroxyethyl- or glycidyl-functional monomer would yield polymers with xcfx89-hydroxy or xcfx89-epoxy groups, respectively.
This method enables the versatility and robustness of the cobalt technology to be utilized to form macromonomers that are comprised predominantly of monosubstituted monomers. Additionally, it provides the key step in a new and less expensive route to end-functional and block or graft copolymers based on monosubstituted monomers. Copolymerizations of monosubstituted monomers with other xcex1-methylvinyl monomers (for example xcex1-methylstyrene) in the presence of cobalt are contemplated.
The choice of the xcex1-methylvinyl comonomer is important in macromonomer synthesis. It must be chosen so that the reactivity towards cobalt (xe2x80x9ccatalytic chain transfer constantxe2x80x9d) of the derived propagating species is substantially greater than that of the propagating species derived from the monosubstituted monomer.
Two factors influence this reactivity.
a) The rate of the chain transfer reaction between the propagating species and the cobalt complex;
b) The relative concentrations of the propagating species. This is determined not only by the monomer concentration but also by the propagation rate constants and reactivity ratios.
While methacrylate esters can be used as xcex1-methylvinyl comonomers (see examples), in copolymerization with styrene, the values of the reactivity ratios and propagation rate constants will favor the formation of styryl chain ends. The product then has an internal rather than the desired terminal double bond. Methacrylate esters are acceptable comonomers in, for example, acrylate polymerizations.
Thus, the use of xcex1-methylvinyl comonomers (for example, xcex1-methylstyrene, methacrylonitrile) which have low propagation rate constants and high chain transfer rate constants are preferred.
There are substantial cost improvements over alternative technologies which involve the use of stoichiometric amounts of an organic transfer agent. The ability to use acrylate/styrenic rich macromonomers, in contexts similar to those developed for methacrylate monomer products by cobalt mediated processes, for example, in graft, star, block and branched copolymer syntheses, further extends the value of the process.
The nature of the derived products changes as a function of time. In the initial stages, the product 
can be obtained as essentially the only product. If the cobalt CTC catalyst levels are relatively low then CTC does not occur after every B-monomer insertion and the product mixture can include: 
Later in the course of the reaction, when the concentration of the two above products is increased, they can be reincorporated into a growing polymer chain. Thus, the product 
where Z can include xe2x80x94H, xe2x80x94CH3, CH2CHYCH3, CH2CMeYCH3, or 
is obtained. In the early stages of the reaction, Z is most often H, but as the reaction proceeds toward 90% conversion, Z begins to include more of the higher molecular weight species as branches. At conversions above 95%, branches begin to appear on the branches, and the polymer becomes hyperbranched as conversions approach 100%.
Metal complexes are those that give catalytic chain transfer with xcex1-methylvinyl monomers. Examples include, but are not limited to, cobalt(II) and cobalt(III) chelates: 
L can be a variety of additional neutral ligands commonly known in coordination chemistry. Examples include water, amines, ammonia, phosphines, The catalysts can also include cobalt complexes of a variety of porphyrin molecules such as tetraphenylporphyrin, tetraanisylporphyrin, tetramesitylporphyrin and other substituted species.
xcex1-Methylvinyl monomers (B monomers) have the general structure 
where Y is as described above in the xe2x80x9cSummaryxe2x80x9d. R is an optionally substituted alkyl (such as fluoroalkyl, hydroxyalkyl, or epoxyalkyl), organosilyl, or aryl group. Preferred examples of xcex1-methylvinyl monomers (B monomers) include methacrylate esters, xcex1-methylstyrene and methacrylonitrile.
xe2x80x9cAxe2x80x9d monomers have the general structure: 
where Y is as described above in the xe2x80x9cSummaryxe2x80x9d.
The enhanced utility of the polymerization method discussed in this invention is that it extends each of these general CTC methodologies:
i) molecular weight control is extended from methacrylates and styrenes to include acrylates, vinyl esters, and other higher activity monomer species;
ii) macromonomer synthesis is extended to the monomers in (i) while retaining the desirable vinyl termination of the resulting species;
iii) end-functional polymer synthesis is also extended to the monomers in (i);
iv) the use of macromonomers as chain transfer agents is extended to include monomer classes heretofore unavailable through CTC technology; and
v) not only are a wider range of block and graft copolymers available through the use of CTC technology, but now it is possible to prepare branched and even hyperbranched species through single-pot reactions.
It is preferred to employ free-radical initiators and solvents in the process of this invention. The process can be run in batch, semi-batch, continuous, bulk, emulsion or suspension mode.
Most preferred A-monomers are:
methyl acrylate, ethyl acrylate, propyl acrylate (all isomers), butyl acrylate (all isomers), 2-ethylhexyl acrylate, isobornyl acrylate, acrylic acid, benzyl acrylate, phenyl acrylate, acrylonitrile, glycidyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate (all isomers), hydroxybutyl acrylate (all isomers), diethylaminoethyl acrylate, triethyleneglycol acrylate, N-tert-butyl acrylamide, N-n-butyl acrylamide, N-methyl-ol acrylamide, N-ethyl-ol acrylamide, trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, tributoxysilylpropyl acrylate, dimethoxymethylsilylpropyl acrylate, diethoxymethylsilylpropyl acrylate, dibutoxymethylsilylpropyl acrylate, diisopropoxymethylsilylpropyl acrylate, dimethoxysilylpropyl acrylate, diethoxysilyipropyl acrylate, dibutoxysilylpropyl acrylate, diisopropoxysilylpropyl acrylate, vinyl acetate, styrene, diethylamino styrene, P-methylstyrene, vinyl benzoic acid, vinylbeuzinsulfonic acid, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl chloride, vinyl fluoride, vinyl bromide.
Most preferred B-monomers are:
methyl methacrylate, ethyl methacrylate, propyl methacrylate (all isomers), butyl methacrylate (all isomers), 2-ethylhexyl methacrylate, isobornyl methacrylate, methacrylic acid, benzyl methacrylate, phenyl methacrylate, methacrylonitrile, alpha methyl styrene, trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, tributoxysilylpropyl methacrylate, dimethoxymethylsilylpropyl methacrylate, diethoxymethyl-silylpropylmethacrylate, dibutoxymethylsilylpropyl methacrylate, diisopropoxymethylsilylpropyl methacrylate, dimethoxysilylpropyl methacrylate, diethoxysilylpropyl methacrylate, dibutoxysilylpropyl methacrylate, diisopropoxysilylpropyl methacrylate, isopropenyl butyrate, isopropenyl acetate, isopropenyl benzoate, isopropenyl chloride, isopropenyl fluoride, isopropenyl bromideitaconic aciditaconic anhydridedimethyl itaconate, methyl itaconateN-tert-butyl methacrylamide, N-n-butyl methacrylamide, N-methyl-ol methacrylamide, N-ethyl-ol methacrylamide, isopropenylbenzoic acid (all isomers), diethylamino alphamethylstyrene (all isomers), para-methyl-alpha-methylstyrene (all isomers), diisopropenylbenzene (all isomers), isopropenylbenzene sulfonic acid (all isomers), methyl 2-hydroxymethylacrylate, ethyl 2-hydroxymethylacrylate, propyl 2-hydroxymethylacrylate (all isomers), butyl 2-hydroxymethylacrylate (all isomers), 2-ethylhexyl 2-hydroxymethylacrylate, isobornyl 2-hydroxymethylacrylate, and TMI(copyright) dimethyl Meta-Isopropenylbenzyl Isocyanate.
Preferred C monomers are those from the list of A monomers minus the styrenic family.
Preferred D monomers include the following styrenes:
styrene, vinyl benzoic acid (all isomers), diethylamino styrene (all isomers), para-methylstyrene (all isomers), and vinyl benzene sulfonic acid (all isomers),
Typical products of the reaction at lower conversions include the linear products from methyl acrylate and methyl methacrylate: 
from butyl acrylate and alpha-methylstyrene: 
from hydroxyethyl acrylate and alpha-methylstyrene: 
from vinyl benzoate and butyl methacrylate: 
Typical products of the reaction at lower conversions include the linear products from butyl acrylate and methyl methacrylate: 
from methyl acrylate and alpha-methylstyrene: 
When the polymerization (for example butyl acrylate as A-monomer and methyl methacrylate as B-monomer) is carried out in the presence of a nonpolymerizable olefin such as 2-pentenenitrile, the product in the initial stages of the polymerization will be: 
and later in the polymerization, the product will be: 
It becomes impractical to draw schematics of any of the higher degrees of branching that are obtained as the conversion of the polymerization approaches 100%.
Oligomers, macromonomers and polymers made by the present process are useful in a wide variety of coating and molding resins. Other potential uses can include cast, blown, spun or sprayed applications in fiber, film, sheet, composite materials, multilayer coatings, photopolymerizable materials, photoresists, surface active agents, dispersants, adhesives, adhesion promoters, coupling agents, compatibilizers and others. End products taking advantage of available characteristics can include, for example, automotive and architectural coatings or finishes, including high solids, aqueous or solvent based finishes. Polymers, such as those produced in this invention, will find use in, for example, structured polymers for use in pigment dispersants.
K+IDS mass spectroscopy is an ionization method that produces pseudomolecular ions in the form of [M]K+ with little or no fragmentation. Intact organic molecules are desorbed by rapid heating. In the gas phase, the organic molecules are ionized by potassium attachment. Potassium ions are generated from an aluminosilicate matrix that contains K2O. All of these experiments were performed on a Finnegan Model 4615 GC/MS quadrupole mass spectrometer (Finnegan MAT (USA), San Jose, Calif.). An electron impact source configuration operating at 200xc2x0 C. and a source pressure of  less than 1xc3x9710xe2x88x926 torr was used. MALDI was also performed on this instrument.
All MW and DP measurements were based on gel permeation chromatography (GPC) using styrene as a standard.
The following abbreviations have been used and are defined as:
TAPCo=meso-tetra(4-methoxyphenyl)porphyrin-Co; VAZO(copyright)-88=1,1xe2x80x2-azobis(cyclohexane-1-carbonitrile) (DuPont Co., Wilmington, Del.); VRO-110=2,2xe2x80x2-azobis(2,4,4-trimethylpentane) (Wako Pure Chemical Industries, Ltd., Osaka, Japan);
DP=degree of polymerization. Mn is number average molecular weight and Mw is weight average molecular weight. AIBN is azoisobutyronitrile. THF is tetrahydrofuran. MA=methylacrylate.